Small base dies for 308 in an AR

bihj said:
You already have the dies.... Try them, if the experiment doesn't work, proceed with a different plan.
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+1

OP, what are your rounds going into? The only place I could see the need for a SB die would be a semiauto with a tight chamber. FWIW, I handload .308 for 1 each, semiauto, lever-action, and bolt action, and I have never had a need for a SB die.
 
jmorris! Spoken like the talented machinist he is. ;)

However, finding a jmorris in my neck of the woods isn't an easy endeaver. The other answer, without such a resource handy, is it depends. I was lucky with my Remington SR25 camouflaged hunting AR with a chamber near the minimum specs for "accuracy". It would feed Remington factory all day. It would not autofeed factory Federal blue box at all. (Its been my practice to buy and shoot factory, to get brass to reload) My Remington reloads with a regular RCBS die set, duplicated the Federal. I bought an RCBS small base set, and those reloads fed as well as the Remington. So depends on your dies and your rifle.....only testing will tell, and only you can decide to change the dies or change the chamber. That said, in most cases new small based dies are cheaper than new chambers....unless you are jmorris-like! Me? Not so much....I used a lathe in a collage class, once. :)

Some will cry, small based dies over size and shorten life. AR's, by their nature, shorten case life....so if that's the desider, sell the rifle and buy a bolt action. I've been VERY happy with my decision.....works great for me.

Bottom line for me is small-based dies are super insurance to see that gas guns feed perfect....every time. I wouldn't be without my .223 and .308 RCBS small-based dies.
 
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I had to buy a small base die for my M1A reloads. I have also nave had to use a small base die on some new factory loads. I don't think the quality of brass is what it used to be years ago.
 
I use LC Brass only. When I got a bunch one fired back a few years, some of it when resized with my regular dies wouldn't fit in my then AR10 or was really hard to close the bolt on my 700 Milspec. I used a small base to fix the brass, not my rifle. After the Small base, the brass would then chamber without an issue. After using the small base that single time, I haven't had to use it again. You don't know, til you know. And you'll know right away.
 
1) What is your common source for brass? If you are reclaiming range picked brass, fired in some other rifle, then having a small base die to at least ONE time resize the bodies to minimum spec is a smart idea. If you are shooting either brass which came from factory ammo only ever fired in this rifle, or shooting manufactured reloaders brass which is only ever fired in this rifle, your opportunity for oversized base issues is much, much lower.

2) Is your 308 LFAR grossly overgassed and unlocking early? Pull the extractor from your bolt and rechamber a fired piece of brass, will the bolt close freely? If your rifle is stretching brass beyond its own chamber dimension because it is overgassed, then you will likely benefit from a small base die (and should really add an AGB to throttle gas to stop your rifle from beating up brass). Most AR’s are overgassed to promote reliability, and most AR builders under-mass the reciprocating assembly, so it’s pretty common to see excessive web expansion and headspace stretch in AR’s - if yours does this, you’ll want an SB die.

3) Do you plan to transfer your brass from this barrel to another barrel, either to use in a different rifle, or to continue using the same brass in this rifle when you replace the barrel? If yes, then most likely you will want an SB die.

***Note: most SB dies are small EVERYWHERE, and sizing the bases back to minimum spec will also mean you’ve pushed the shoulder back too far, creating excessive headspace which may lead to case separations/failures, or may cause ignition problems. Equally, the SB dies may result in undersized necks, creating excessive neck tension, which can cause shoulder collapses or worse, slight bulges which go unnoticed, until the rounds refuse to chamber. As I discussed in a couple of other threads this week, it is much better to cut the shoulder and neck out of the small base die and use it ONLY as a small base BODY ONLY die. When we small base size, we are really trying to influence only ONE dimension of the brass - the base diameter - but most SB dies will smush every dimension to minimum spec, which can cause multiple other problems, so making the SB die into truly ONLY an SB die is the better move.
 
Varminterror said:
it is much better to cut the shoulder and neck out of the small base die and use it ONLY as a small base BODY ONLY die. When we small base size, we are really trying to influence only ONE dimension of the brass - the base diameter - but most SB dies will smush every dimension to minimum spec, which can cause multiple other problems, so making the SB die into truly ONLY an SB die is the better move.
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One of the shortcuts to that is to size .308 brass in a .30-06 die... it sizes the body all the way down, without doing anything with the neck, then continuing on with a normal .308 sizer. That's one of the hot setups when processing machine gun fired brass... supposedly.
 
Charlie98 said:
One of the shortcuts to that is to size .308 brass in a .30-06 die... it sizes the body all the way down, without doing anything with the neck, then continuing on with a normal .308 sizer. That's one of the hot setups when processing machine gun fired brass... supposedly.
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Not a rabbit I would chase. Doing so works by the same principle as any small base die - if you make everything small enough to fit, it’ll fit, but that doesn’t actually mean the brass is appropriately sized for the chamber, and using a 30-06 die makes 308win brass too small at the shoulder.

Sizing 308win brass with a .30-06 die undersizes the 308 shoulder by ~7 thou, because the 30-06 die is smaller diameter along the body at the position of the 308 shoulder than would be a 308win die. This means sizing 308win brass in a .30-06 die is notably changing the body taper, which has to blow back out in firing - sure, it’ll feed really well, because it is undersized at every part of the body… but under sizing every part of our body is contraindicated for making accurate ammo. Especially as we’re changing our internal volume for that sizing event. Just a bad idea all around.

Equally, the base of the .30-06 is only 1/2 thou smaller than that of the .308, so a 30-06 really isn’t a great small base diameter for a 308, unless the 30-06 is already a small base ‘06 die.

I was given the same advice when I swapped from a Garand to an M1A for SR, until I mentioned it to my mentor and he pointed out the problems with the idea. He contended that simply sizing twice in a 308win die did the exact same thing to the base diameter as sizing in a 30-06 die first, but didn’t come with the problems of under sizing the shoulder and changing the body taper.

Not a rabbit I would chase, and I don’t recommend it to anyone else either.
 
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Varminterror said:
I was given the same advice when I swapped from a Garand to an M1A for SR, until I mentioned it to my mentor and he pointed out the problems with the idea. He contended that simply sizing twice in a 308win die did the exact same thing as sizing in a 30-06 die first.
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:thumbup:
 
Just get a 308 Win small base die, or otherwise, some sunny day, you will be kicking the charging handle to extract an unfired case that won't go in the chamber. And buy case gauges to ensure you are setting the shoulder back 0.003"

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You can call die manufacturer's and they will tell you small base dies size the case head 0.002" more than standard sizing dies.

Sometimes, small base dies won't reduce the head sufficiently and that is when you spend a thousand for a roll sizer



The casepro100 site is gone so maybe the company has gone bust. But never fear, there are alternatives

https://www.doublealpha.biz/us/combo-rollsizer-automatic-decapper-drop-tube-decappinp-pins
 
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Having used Dillon rifle dies (which are small base) for years without any issues, I find much of what is stated in this thread to to be incorrect. So, why is that?
 
I've never needed them. I've have loaded a lot of tight match chamber rifles over the year and never had a problem. Now if you trying to size MG shot brass, it's going to require some work. Annealing the neck shoulder area will make the process go a lot smoother.
 
I still haven't been satisfied by not using the easy and cheep Lee 45acp bulge buster die. It won't touch anything but the base of the case exactly where the claimed problem is.
 
For my semi-auto rifles, I use small base dies if one is available.

Otherwise, I get really picky about my source of brass.

This is no fun. Been there, done that.

Slamfire said:
Just get a 308 Win small base die, or otherwise, some sunny day, you will be kicking the charging handle to extract an unfired case that won't go in the chamber.
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One of these days I need to get a Sheridan case gauge for some cartridge, probably 223 Rem, just to see what all the hub bub is about.

Dillon and L E Wilson case gauges have their uses but are cut generously in the body dimension. They are not good chamber gauges. (Check the manufacturer’s fine print).

Before I got into multiple rifles chambered for the same cartridge, standard dies worked fine for cases fired in my rifles.

But I have several 223 Rem/5,56 Nato chamberings that cause me problems with chambering with standard dies. I’m guessing an accumulation of tolerance error.

So, pays your money and take your chances when it comes to reloading for semi-auto rifles.

It is definitely not a “cut and dried”’ world.
 
I load and shoot in excess of 5k rounds a year out of match and standard chambered semi-autos - 223, 308, and 30-06 - and have never owned or loaded with a small base die.

I have however had .005" removed from the bottom of both of my Forster sizers (223 and 308) so that I can size fired brass down to work in match chambers cut between .000" and .0015" of minimum headspace.
 
Plano11 said:
I load and shoot in excess of 5k rounds a year out of match and standard chambered semi-autos - 223, 308, and 30-06 - and have never owned or loaded with a small base die.

I have however had .005" removed from the bottom of both of my Forster sizers (223 and 308) so that I can size fired brass down to work in match chambers cut between .000" and .0015" of minimum headspace.
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I love forester dies, and a lot of their sizers are small base. The national match series has reduced dementions depending on which one you get.
 
guzzi said:
Having used Dillon rifle dies (which are small base) for years without any issues, I find much of what is stated in this thread to to be incorrect. So, why is that?
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Gunwriters. Plain and simple. These guys did not use cartridge headspace gauges, at best they sized to the shell holder plus an 1/8 turn, and started having case head separations with small base dies. And they told the world that small base dies are not necessary and that small base dies "over size" brass. Well guess what, I have had small base dies that would set the shoulder back excessively if I turned to the shell holder plus an 1/8 turn. And guess what, I did not do that as I used cartridge case headspace gauges to measure how much I set my shoulder back.

If you cannot measure a phenomenon, you cannot understand the phenomenon, nor can you control the phenomenon.

For decades Gunwriter Mike Venturino has been one that claimed that small base dies excessively sized brass and that only standard sizing dies were needed for gas guns. But in the July 2012 issue of Guns Magazine, he was testing an M1a and a AR10 and his reloads are too tight. I find it humorous to read that he had to beat the bolts open with scrap lumber. Ha, Ha.At least he learned, now he mentions his mistake and recommends small base sizing dies. He is however, an exception.

The inprint crowd consistently disappoint and propagate nonsense. Anyone remember the infallible Hatcher Index of stopping power? Was in all the magazines. Sold a lot of 45's. Now that 9mm is outselling everything else, don't read about the Hatcher Index anymore.
 
Dillon dies have minimum base dia spec. That doesn’t mean they have minimum dimensions at all positions.

Lee dies do as well, as standard.

I small base size brass any time I transfer a batch from one barrel to another. When I don’t, sometimes I end up with bolt click, sticky feeding, or sticky extraction. As an example, I didn’t small base size my 6 creed a few months ago when I changed barrels, and I paid dearly for it - even with very low end loads, I got heavy bolt lift. My hand was bruised after ~50rnds of slapping the bolt open. Changing NOTHING else, except running through my small base body die - a modified RCBS small base die - all of those issues went away in the second batch, and all rounds thereafter.
 
Larry in wyoming said:
Thanks for all of the replies. I'll just have to see how it goes I guess.
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Maybe you'll be one of the lucky ones with your particular weapon. Maybe not. I have home insurance, and car insurance, and business insurance......and with small-based dies I have ammo insurance. ;) The best part is my AR ammo is also insurance against threats to my family.....and I know it's dependable even if I change weapons or buy a new one. That's worth more than a little to me.
 
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It's not in stone that you "have" to have a small base die. Some of my AR's in 5.56 and .308 are perfectly happy without it, and some are picky. I bought a rollsizer, so no longer worry about using a small base die, but before the rollsizer...I used a standard RCBS die for my .308 bolt guns, and a standard RCBS die for my .223 bolt guns, and dillon dies (which are small base dies) for bulk ammo meant for the AR's. If you recover brass from a machine gun shoot, or brass fired on military ranges, you really need to either roll size or use a small base die if you need to be 100% certain it will run in ANY gun, not just yours. Just been my experience.
 
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